Asthma and COPD Q 15 - Gyan Darpan : Learning Portal
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Sunday 24 April 2022

Asthma and COPD Q 15

A client with emphysema should receive only 1 to 3 L/minute of oxygen if needed, or he may lose his hypoxic drive. Which of the following statements is correct about hypoxic drive?
     A. The client doesn’t notice he needs to breathe.
     B. The client breathes only when his oxygen levels climb above a certain point.
     C. The client breathes only when his oxygen levels dip below a certain point.
     D. The client breathes only when his carbon dioxide level dips below a certain point.

Correct Answer: C. The client breathes only when his oxygen levels dip below a certain point.

Clients with emphysema breathe when their oxygen levels drop to a certain level; this is known as the hypoxic drive. In the meantime, his carbon dioxide levels continue to climb, and the client will pass out, leading to a respiratory arrest. The hypoxic drive theory then goes on to say that if the healthcare provider gives these patients too much oxygen they blunt their hypoxic drive. As their chemoreceptors are already tolerant of high levels of carbon dioxide, and therefore they have also lost that drive, their respirations will begin to slow causing a further rise in carbon dioxide levels, and a consequent acidosis.

Option A: They don’t take a breath when their levels of carbon dioxide are higher than normal, as do those with healthy respiratory physiology. COPD patients tend to have chronically elevated levels of carbon dioxide due to the nature of their illness. The theory goes then that because of this chronically elevated level of carbon dioxide in the chemoreceptors become tolerant of these high levels and therefore the carbon dioxide ceases to be that person’s drive to breathe. What therefore drives them to breathe is the hypoxic drive or the lower levels of oxygen.
Option B: If too much oxygen is given, the client has little stimulus to take another breath. The peripheral chemoreceptors are sensitive to the levels of oxygen in the body. They will send a signal to breathe when the partial pressure of oxygen begins to fall. This is referred to as the hypoxic drive but this drive has a much more minor role in breathing.
Option D: The central chemoreceptors monitor carbon dioxide levels in the body. When those carbon dioxide levels are high a signal is sent to speed up the drive to breathe to blow off the excess carbon dioxide. So the levels of carbon dioxide dictate how fast we will breathe.

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